Java Collections reverseOrder() Method

The reverseOrder() is a Java Collections class method which returns a comparator that imposes the reverse of the natural ordering on the objects. There is two different types of Java reverseOrder() method which can be differentiated depending on its parameter. These are:

Java Collections reverseOrder() Method
Java Collections reverseOrder(comp) Method

Java Collections reverseOrder() Method

The reverseOrder() method of Java Collections class is used to get the comparator that imposes the reverse of the natural ordering on a collection of objects which implement the Comparable interface.

Java Collections reverseOrder(comp) Method

The reverseOrder() method of Java Collections class is used to get the comparator that imposes the reverse ordering of the specified comparator.

Syntax

Following is the declaration of reverseOrder() method:

public static <T> Comparator<T> reverseOrder()
public static <T> Comparator<T> reverseOrder(Comparator<T> comp)

Parameter

Parameter	Description	Required/Optional
comp	It is a comparator whose ordering is to be reversed by the returned comparator or null.	Required

Returns

Method	Returns
reverseOrder()	It returns a comparator that imposes the reverse natural ordering on a collection of objects that implement the Comparable interface.
reverseOrder(Comparatorcomp)	It returns a comparator that imposes the reverse ordering of the specified comparator.

Exceptions

Compatibility Version

Java 1.5 and above

Example 1

import java.util.*;
public class CollectionsReverseOrderExample1 {
	public static void main(String[] args) {		       
		//Create linked list object
	      LinkedList<Integer> list = new LinkedList<Integer>();
	      //Add values in the list
	      list.add(10);
	      list.add(-20);
	      list.add(50);
	      list.add(90);
	      list.add(-15);
	      //Sort the list and return comparator for reverse order
	      Collections.sort(list, Collections.reverseOrder());  
	      System.out.println("List sorted in ReverseOrder: ");
	      System.out.println(list);
	      }
}

Test it Now

Output:

List sorted in ReverseOrder: 
[90, 50, 10, -15, -20]

Example 2

import java.util.*;
public class CollectionsReverseOrderExample2 {
	public static void main(String[] args) {		       
		//Create Array list object
		List<String> list = Arrays.asList("Java", "Python", "Ruby", "COBOL");
            Collections.sort(list, Collections.reverseOrder());
	      System.out.println("List sorted in ReverseOrder: ");
	      System.out.println(list);
	      }
}

Test it Now

Output:

List sorted in ReverseOrder: 
[Ruby, Python, Java, COBOL]

Example 3

import java.util.*;
public class CollectionsReverseOrderExample3 {
	public static void main(String[] args) {		       
		//Create Array list object
		List<String> list = Arrays.asList("Jaya", "Pratham", "Ruby", "Commit");
		Collections.sort(list, Collections.reverseOrder (CollectionsReverseOrderExample3::lastCharComparator));
		//Sort the list according to last character of word and return comparator for reverse order
        System.out.println(list);
        }
	private static int lastCharComparator(String s1, String s2) {
		return Character.compare(s1.charAt(s1.length() - 1), s2.charAt(s2.length()-1));
		}
}

Test it Now

Output:

[Ruby, Commit, Pratham, Jaya]

Example 4

import java.util.*;
public class CollectionsReverseOrderExample4 {
	public static void main(String[] args) {		       
		//Create linked list object  	   
	      LinkedList<Integer> list = new LinkedList<Integer>();  
	      //Add values in the list 
	      list.add(50);  
	      list.add(-20);  
	      list.add(120);  
	      list.add(-80);  
	      //Sort the list and Create comparator for reverse order
	      Comparator<Integer> cmp = Collections.reverseOrder(null);  
	      Collections.sort(list, cmp);  
	      //Print the list
	      System.out.println("List sorted in ReverseOrder: ");      
	      for(int i : list) {
	         System.out.println(i+ " ");
	      }	
	}
}

Test it Now

Output:

List sorted in ReverseOrder: 
120 
50 
-20 
-80

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Java Collections reverseOrder() Method